A need exists for additional methods for preparing fused oxazinones. Such compounds include intermediates for the preparation of crop protection agents, pharmaceuticals and other fine chemicals.
Fused oxazinones have been prepared by a variety of methods. For example, N-acylanthranilic acids have been treated with acetic anhydride, anthranilic acids have been treated with carboxylic acid anhydrides, and anthranilic acids and carboxylic acids have been coupled in the presence of various dehydrating agents (see G. M. Coppola, J. Heterocyclic Chemistry 1999, 36, 563-588). Fused oxazinones have also been prepared by treatment of ortho-amino carboxylic acids with carboxylic acid chlorides in the presence of base (see e.g., Jakobsen et al., Biorganic and Medicinal Chemistry 2000, 8, 2803-2812 and Jakobsen et al., Biorganic and Medicinal Chemistry 2000, 8, 2095-2103). Benzoxazinones have also been prepared by treatment of a carboxylic acid with a sulfonyl chloride and then treatment with an anthranilic acid (see D. V. Ramana and E. Kantharaj, Org. Prep. Proced. Int. 1993, 25, 588).